Wireless networks enter a new era in which various objects, such as mobile phones, computers, vehicles, watches, are automatically and intelligently connected to provide ubiquitous services. Green communication protocols are required to save energy consumption and improve transmission performance. MAC protocols can detect the signal status and energy consumptions of physical channels to adapt to the dynamic wireless conditions. They can also provide node-to-node transmissions for network layer protocols under green wireless networks. The thesis presents three energy efficient communication solutions under different delay-tolerant networks scenarios to study the efficiency of MAC transmission protocols within wireless networks: CPMAC, AFLAS and TREE. CPMAC applies three energy-aware algorithms to transmit different quality requirements of data within one contact interval in sparsely connected sensor networks. Simulations and analysis shows CPMAC outperforms two other important MAC protocols in wireless sensor networks and vehicular ad-hoc networks in throughput, delay, energy consumption. AFLAS uses an adaptive frame length aggregation scheme for Vehicular Networks that is designed to improve transmission efficiency and increase data throughput. Suitable aggregation frame lengths are calculated according to the current wireless status, and applied in the MAC layer at the onset of data transmissions to save overhead and energy consumption. The simulations of AFLAS exhibit a significant improvement results in data throughput, retransmissions, overheads and transmission efficiency in comparison to non-adaptive aggregation schemes. TRaffic adaptive Energy Efficient MAC protocol (TREE) adapts its work modes: reservation and contention mode, to traffic density and adjusts its duty cycle to achieve energy efficiency. TREE demonstrates better performance in terms of energy efficiency and traffic adaptability than the schedule-based MAC protocol TDMA, the contention-based protocol CSMA and the traffic adaptive protocol TRAMA under mobile sensor network environments. By studying and designing MAC protocols in wireless environments, the thesis shows the comprehensive knowledge and principles of communication protocol designs with latency relaxed. Future work is discussed for further designs and implementations of green communication protocols.